1. Field of the Invention
The present invention relates to a composition for use in the oral cavity, which can disinfect bacteria in the oral cavity, has a reduced bitter or astringent taste, and is useful for the prevention or treatment of oral diseases such as dental caries, periodontosis, and the like.
2. Description of Background Art
Dental caries and periodontosis (e.g., gingivitis, periodontitis), which are typical diseases in the oral cavity are a type of bacterial infection. Dental caries is considered to be caused by Streptococcus mutans, gingivitis by Actinomyces viscosus, and periodontitis by Prophyromonas gingivilis, Capnocytophaga ochracea, and the like.
Accordingly, compositions for oral cavity comprising an antibacterial agent for these bacteria had been developed for the prevention of dental caries and periodontosis, which are commercially available. Examples of such compositions include dentifrices, mouthwashes, and the like, in which a cationic antibacterial compound (e.g., chlorhexidine hydrochloride, cetylpyridinium chloride), a nonionic antibacterial compound (e.g., triclosan), or the like, is incorporated.
However, many of the conventional cationic antibacterial agents give a bitter and astringent taste when incorporated in an amount effective for the disinfection. For example, Yamazaki, et al reports that a gargle comprising 0.04% by weight of benzalkonium chloride is not suitable for common use, since it provides an extremely bitter and astringent taste, even though its effect is remarkable ["Oral cavity disinfection effect of benzalkonium chloride", Journal of Dental Critics, 554, 227 (1988)]. Furthermore, these cationic antibacterial compounds decrease their disinfection effects in the presence of an anionic surfactant in a mouthwash composition. Therefore, their use in combination with a nonionic surfactant was proposed (e.g., Japanese Patent Laid-open (kokai) Nos. 101417/1984, 101418/1984, 282317/1990, 109315/1991). The proposed compositions, however, not only failed to improve the taste, but also provided insufficient disinfection effects due to the poor immediate antibacterial effect exhibited by conventional nonionic antibacterial compounds. Thus, the compositions had a drawback in that they could not exhibit sufficient antibacterial actions during use.
UK Patent No. 1,431,932 discloses a composition for use in the oral cavity for suppressing formation of dental calculus and dental stone, comprising an antibacterial compound which consists of 2 mols of a quaternary ammonium compound and 1 mol of a monoalkyl phosphate. This composition for use in the oral cavity, however, exhibits no prolonged antibacterial effect and does not provide an improved taste. On the other hand, as compositions for use in the oral cavity to Which a phosphate type surfactant is added, Japanese Patent Laid-open (kokai) No. 47542/1978 (U.S. Pat. No. 4,152,421) discloses a dentifrice comprising a monoalkyl phosphate as a foaming agent, which the inventors claim does not change taste of foods and beverages; Japanese Patent Publication (kokoku) No. 500061/1979 (U.S. Pat. No. 4,366,146) proposes a dentifrice for preventing formation of spots comprising a monoalkyl phosphate as a film forming material; and U.S. Pat. No. 4,036,950 discloses a composition for use in the oral cavity having a pH of above 6 and comprising an abrasive, a cationic antibacterial compound, and a polyoxyethylene-alkylether phosphate. Of these publications, Japanese Patent Laid-open (kokai) No. 47542/1978 and Japanese Patent Publication (kokoku) No. 500061/1979 does not mention the combined use of a cationic surfactant and a phosphate, and the composition proposed in U.S. Pat. No. 4,036,950 provides only insufficient improvement in its taste.
Japanese Patent Laid-open (kokai) No. 218605/1990 describes a composition comprising a quaternary ammonium compound and a salt of phosphoric ester and effective as an antibacterial and antiseptic agent for use in the skin or the hair. The specification, however, does not suggest at all the possibility of applying the proposed composition to the oral cavity.
An object of the present invention is to provide a composition for use in the oral cavity which exhibits an immediate and long-continued antibacterial activity to bacteria in the oral cavity, provides a good taste, and does not reduce its antibacterial activity even when a surfactant as a detergent is added.
The inventors of the present invention have undertaken painstaking investigations and found that a composition comprising a specific antibacterial compound and a vehicle for use in the oral cavity provides little bitter or astringent taste, has an excellent antibacterial activity, and exhibits an immediate and long-lasting continued antibacterial effect, even if a surfactant is added. This finding has led to the completion of the present invention.